The present invention relates to a process for coating paper, wherein the coating material used is a biodegradable, aliphatic-aromatic polyester comprising:                i) from 40 to 70 mol %, based on the components i to ii, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid and brassylic acid;        ii) from 60 to 30 mol %, based on the components i to ii, of a terephthalic acid derivative;        iii) from 98 to 102 mol %, based on the components i to ii, of a C2-C8-alkylenediol or C2-C6-oxyalkylenediol;        iv) from 0.00 to 2% by weight, based on the total weight of components i to iii, of a chain extender and/or crosslinking agent selected from the group consisting of: a di- or polyfunctional isocyanate, isocyanurate, oxazoline, epoxide, carboxylic anhydride and/or an at least trifunctional alcohol or an at least trifunctional carboxylic acid;        v) from 0.00 to 50% by weight, based on the total weight of the components i to iv, of an organic filler selected from the group consisting of: native or plasticized starch, natural fibers, wood meal and/or an inorganic filler selected from the group consisting of: chalk, precipitated calcium carbonate, graphite, gypsum, conductive carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc, glass fibers and mineral fibers and        vi) from 0.00 to 2% by weight, based on the total weight of the components i to iv, of at least one stabilizer, nucleating agent, lubricant and release agent, surfactant, wax, antistatic agent, antifogging agent, dye, pigment, UV absorber, UV stabilizer or other plastics additive;        
and having a melt volume rate (MVR) according to EN ISO 1133 (190° C., 2.16 kg weight) of from 3 to 50 cm3/10 min.
The invention furthermore relates to a process for coating paper, wherein the coating material used is a polymer mixture comprising:                from 5 to 95% by weight of a biodegradable, aliphatic-aromatic polyester obtainable by condensation of:                    i) from 40 to 70 mol %, based on the components i to ii, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid and brassylic acid;            ii) from 60 to 30 mol %, based on the components i to ii, of a terephthalic acid derivative;            iv) from 98 to 102 mol %, based on the components i to ii, of a C2-C8-alkylenediol or C2-C6-oxyalkylenediol;            iv) from 0.00 to 2% by weight, based on the total weight of components i to iii, of a chain extender and/or crosslinking agent selected from the group consisting of: a di- or polyfunctional isocyanate, isocyanurate, oxazoline, epoxide, carboxylic anhydride and/or an at least trifunctional alcohol or an at least trifunctional carboxylic acid;            v) from 0.00 to 50% by weight, based on the total weight of the components i to iv, of an organic filler selected from the group consisting of: native or plasticized starch, natural fibers, wood meal and/or an inorganic filler selected from the group consisting of: chalk, precipitated calcium carbonate, graphite, gypsum, conductive carbon black, iron oxide, calcium chloride, dolomite, kaolin, silicon dioxide (quartz), sodium carbonate, titanium dioxide, silicate, wollastonite, mica, montmorillonite, talc, glass fibers and mineral fibers and            vi) from 0.00 to 2% by weight, based on the total weight of the components i to iv, of at least one stabilizer, nucleating agent, lubricant and release agent, surfactant, wax, antistatic agent, antifogging agent, dye, pigment, UV absorber, UV stabilizer or other plastics additive;            and having a melt volume rate (MVR) according to EN ISO 1133 (190° C., 2.16 kg weight) of from 3 to 50 cm3/10 min;                        
and                from 95 to 5% by weight of one or more polymers selected from the group consisting of: polylactic acid, polycaprolactone, polyhydroxyalkanoate, chitosan, gluten and one or more aliphatic/aromatic polyesters, such as polybutylene succinate, polybutylene succinate adipate or polybutylene succinate sebacate, polybutylene terephthalate-co-adipate;        
and                from 0 to 2% by weight of a compatibilizer, is used.        
WO-A 92/09654, WO-A 96/15173, WO-A 2006/097353 to 56 describe, for example, polybutylene terephthalate succinates, adipates, sebacates, azelaates and brassylates and WO 2006/074815 describes mixtures of these aliphatic-aromatic polyesters with other biodegradable polymers, such as polylactic acid or polyhydroxyalkanoates. The possibility of coating paper with these polymers or polymer mixtures is not explicitly mentioned in these documents.
In the attempts to coat paper with the known polyesters and polyester mixtures, only comparatively thick layers could be produced comparatively slowly.